Next up for Williams, 10th-seeded Sara Errani, the first Italian woman in the tournament since the Open era began in 1968.

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Serena Williams, left, shakes hands with Ana Ivanovic, of Serbia, following their match in the quarterfinal round of play at the U.S. Open tennis tournament.

Updated at 11:54 PM PST on Wednesday, Sep 5, 2012

Serena Williams shared a thought the other three semifinalists in the U.S. Open certainly won't want to hear.

"I feel like I'm going to get more focused and serious and start playing 'Serena tennis,'" she said.

Whatever brand she's been playing so far has been pretty good, too.

Fourth-seeded Williams served 12 aces Wednesday night to bring her total to 41 for the tournament and move to the semifinals with a typically overpowering victory, 6-1, 6-3 over Ana Ivanovic.

Williams got 29 first serves in and won the point on 26 of them. She faced two break points and saved both of them. She has lost a total of 16 games through five matches. When No. 12 Ivanovic held serve to make it 3-1 in the first, it snapped a string of 23 straight games Williams had won, starting at the end of her third-round match last Saturday.

"I think the quality of tennis compared to last year, it was much higher, I think from both of us," said Ivanovic, a 6-3, 6-4 loser to Williams in the fourth round last year. "I mean, she was serving unbelievable. She was hardly missing serves. That puts a lot of pressure on opponents' own service games."

Next up for Williams, 10th-seeded Sara Errani, a 6-2, 6-4 winner over her Italian doubles partner, Roberta Vinci. Errani will be the first Italian woman in the tournament since the Open era began in 1968.

On paper, that semifinal looks like a mismatch, with 5-foot-4 Errani's serve maxing out at 81 mph Wednesday, while 5-9 Williams was consistently in the 110s. But Errani is the French Open runner-up and has lifted her ranking into the top 10 after starting the year at 45.

"A lot will depend on her," Errani said about the matchup. "I will try to play my game, try to get her off balance. I still need to study up and prepare."

Also advancing Wednesday was third-seeded Maria Sharapova, who was trailing 4-0 when play resumed after being suspended because of rain Tuesday. Given nearly 24 hours to think about things, Sharapova rallied for a 3-6, 6-3, 6-4 victory over No. 11 Marion Bartoli. She improved to 12-0 in three-setters this year.

"It's a great statistic," Sharapova said. "It shows that I enjoy the battle no matter what the score is. The third set, it's the last set out there, and there's no reason you shouldn't put everything out there. That's how I treat those situations."

Sharapova will play top-seeded Victoria Azarenka, who got the day off after her three-set victory over defending champion Sam Stosur on Tuesday.

The Williams match was in doubt only for a brief time, with Williams serving in the second set, ahead 4-3. The game went to three deuces. Williams closed it out with a pair of service winners clocked at 119 and 105 mph.

With Ivanovic serving to stay in the match, Williams won the second point of the game, when she hustled to the net to return Ivanovic's dink shot, hit a backhand winner, then skidded and fell on her backside.

"I don't know why that happened," Williams said.

Eight points later, the match was over.

Williams conceded she was distracted in the lead up to the match because she got emotional watching Andy Roddick play. Williams has known Roddick since she was a little kid and was moved by what turned out to be his finale, a four-set loss to Juan Martin del Potro in the match before hers.

Fidgeting with her cell phone during the interview, she said she's been losing focus on and off the court of late and that she'd like to tighten things up as the final weekend approaches.

"I didn't think I came into this tournament playing my best, but I definitely played better in the last two matches," Williams said. "I hope I have two matches left, and, you know, give 200 percent."

Ivanovic, happy with her first Grand Slam quarterfinal appearance since she won the French Open in 2008, was asked if she would be surprised if anyone other than Williams was holding the winner's trophy come the end of the tournament.